The present invention relates to an electrode for the purpose of detecting electro-biophysical phenomena.
Electro-biophysical phenomena indicated by an electrocardiogram, electromyogram, electroencephalogram, etc. are clinically utilized. The biophysical potential of these phenomena is extremely low so that measurement thereof requires a technique somewhat different from that in general electronics measurement. Referring to the electrode for use in said measurement, it is required that the voltage of polarized electrode between the electrode and hypodermal tissues is low, its contact resistance is low, it can maintain a stable contact for a long time, it is free of generation of noises, to wit, change in the voltage of polarized electrode and contact resistance, and it remains in place despite physical movement of the patient.
According to the conventional electrocardiographic measurement, conductive metal plates are stuck on the spots-of-measurement by means of an electrode paste. In the conventional measurement of electroencephalogram, it is usual to paste a plate electrode on the spot-of-measurement or stick a needle electrode therein. In the case of said plate electrode, the electrode comes in contact with just the epidermis, so that the contact resistance becomes high, while in the case of said needle electrode, the electrode penetrates into the hypodermal tissues sufficiently, but the patient would be discomforted at the time of application thereof. Besides, both of these conventional electrode are defective in that the voltage of polarized electrode between the electrode and hypodermal tissues is very high. Accordingly, even a slight slipping-out of position of the electrode of physical movement of the patient would result in wide fluctuations of the voltage of polarized electrode. As the voltage of polarized electrode is fairly higher than the biophysical potential, a stable and exact measurement of biophysical potential is infeasible. As the special method of precision measurement, there is known a method employing an electrode consisting of a pressure-molded mixture of silver powder and silver chloride powder and bringing said electrode into contact with the skin through an electrode paste, which has admittedly proved fairly efficient. However, even in the case of this method, there is generated a voltage of polarized electrode considerably higher than the biophysical potential and even a slight discrepancy between the electrode and the skin would result in wide fluctuations of the voltage of polarized electrode. Accordingly, even when a silver chloride silver surface electrode is employed, an exact measurement cannot be ensured. Not only that, an electrode of this kind is very costly, so that it has not yet come into general use. Various attempts have hitherto been made with efforts centering round the problems of how to minimize the voltage of polarized electrode and how to effect correction with an amplifier in order to minimize the influence of the generated voltage of polarized electrode, but the above discussed defects still remain unremedied.